1. Field of the Invention
This invention relates to a mobile communications system, and communications method therein, for setup communications between terminals where at least the terminals on the receiving end are mobile communications terminals (hereinafter xe2x80x9cmobile terminalsxe2x80x9d), and particularly to a mobile communications system and communications method wherein, when there are communications between mobile terminals, notification of the area occupied by a mobile terminal on the receiving end is made to the terminal on the sending end.
2. Description of the Related Art
FIG. 11 presents an example configuration of a common mobile communications system. In FIG. 11, a situation is presumed wherein a mobile terminal la on the sending end (hereinafter xe2x80x9csending terminalxe2x80x9d) performs a call-up request to a mobile terminal 1b on the receiving end (hereinafter xe2x80x9creceiving terminalxe2x80x9d). A call-up request signal from the sending terminal la is routed through a base station 2a controlling the area occupied by the sending terminal 1a, and through a base station controller 3a controlling a plurality of base stations 2a, and arrives at a switch 4a. The area controlled by a base station 2a is called a cell area (CA), while an area comprising a plurality of CAs under the control of a base station controller 3a is called a location area (LA). The switch 4a controls a plurality of base station controllers 3a. 
The switch 4a accesses an HLR (home location register), finds the switch 4b that controls the area occupied by the receiving terminal 1b, and sends a call-up request signal to the switch 4b. The HLR is a storage device that stores area information in LA units occupied by mobile terminals. That area information is updated every time any of the mobile terminals move between LAs.
Thus the switch 4a finds the switch 4b controlling the And area occupied by the receiving terminal 1b, and performs processing to establish communications between the sending terminal 1a and the receiving terminal 1b, following a common ISDN protocol.
Conventionally, however, notification of the position occupied by the receiving terminal 1b is not made to the sending terminal 1a prior to setup the call. Hence a sending party using the sending terminal 1a is unable to know beforehand the position of the receiving party using the receiving terminal 1b. That being so, in cases, for example, where the position occupied by the receiving party is not where the sending party assumes it to be, and there is no need to establish a call, a problem arises in that a call is established, and a toll is paid, even in cases where the position of the receiving party is far removed from the position of the sending party, and where there is no need to communicate at such a high cost.
It is also conceivable, on the other hand, that the switch 4a will make notification of the LA of the receiving terminal 1b obtained from the HLR. However, since an LA is a broad area roughly equivalent to a prefecture, that is too broad an area for determining the position occupied by the receiving terminal 1b. 
An object of the present invention, therefore, is to provide a mobile communications system and communications method for notifying a sending terminal, prior to setup a call, of area information capable of specifying the position occupied by the receiving terminal.
In order to achieve the object stated above, one aspect of the present invention is that information on the area occupied by a receiving terminal is passed to the sending terminal, prior to setup a call, in units of CAs that are smaller than the LAs described earlier. Accordingly, the position occupied by the sending terminal can be specified, so that calls that are unnecessary due to that position do not have to be made, whereupon unnecessary tolls are avoided.
In order to achieve the object stated above, another aspect of the present invention is a mobile communications system comprising: a first switch; a first terminal accommodated in the first switch; a second switch; a plurality of base stations accommodated in the second switch; and a second terminal that is a mobile terminal present inside (occupying) an area controlled by one base station of the plurality of base stations, wherein the second switch acquires information on the area occupied by the second terminal, from a response of the second terminal to a call based on a call establishment request to the second terminal from the first terminal, and sends the area information to the first switch; and the first switch passes the area information to the first terminal during call setup processing.
In the invention described above, the first switch determines whether or not the first terminal has display functions. When the first terminal does have display functions, the first switch passes signals for displaying the area information to the first terminal, and when the first terminal does not have display functions, the first switch may pass signals for audio-outputting the area information to the first terminal.
In the invention described above, moreover, in a preferable mode thereof, the second switch puts the call setup processing on standby for a prescribed time period following the sending of the area information.
At this time, for example, the first switch will send a call release instruction to the second switch when a call disconnect request is received from the first terminal. The second switch will restart call setup processing when no call release instruction is received within the prescribed time period, and will execute call release processing when a call release instruction is received.
Alternatively, for example, the first switch will send a call setup processing continuation instruction to the second switch when a call setting processing continuation request is received from the first terminal. The second switch will restart call setup processing when a call setup processing continuation instruction is received from the first switch within the prescribed time period, and will execute call release processing when no call setup processing continuation instruction is received.
In the invention described above, furthermore, in another preferable mode thereof, the second switch places call setup processing on standby until a call setup processing continuation instruction is received from the first switch after sending the area information.
At this time, for example, the first switch will send a call setup processing continuation instruction to the second switch when no call disconnect request is received from the first terminal, and will send a call release instruction to the second switch when a call disconnect request is received. The second switch will restart call setup processing when a call setup processing continuation instruction has been received from the first switch, and will execute call release processing when a call release instruction has been received from the first switch.
Alternatively, for example, the first switch will send a call setup processing continuation instruction to the second switch when a call setup processing continuation request has been received from the first terminal, and will send a call release instruction to the second switch when no call setup processing continuation request has been received. The second switch will restart call setup processing when a call setup processing continuation instruction has been received from the first switch, and will execute call release processing when a call release instruction has been received from the first switch.
Furthermore, in order to achieve the object stated above, yet another aspect of the present invention is a method for communicating between a first terminal accommodated in a first switch and a second terminal that is a mobile terminal present inside (occupying) an area controlled by one of a plurality of base stations accommodated in a second switch, comprising the steps of: acquiring information on the area occupied by the second terminal from the response of the second terminal to a call from the second switch based on a call setup request to the second terminal from the first terminal; sending the area information from the second switch to the first switch; and passing the area information from the first switch to the first terminal during call setup processing.